Arm Bones | Bones of the Arm | Learn Bones In anatomy, the entire arm is divided into two regions, the upper portion above the elbow known as the upper arm and the lower portion below the elbow known as the forearm. Sometimes the the entire arm is referred to as the upper limb and the two portions are the arm and forearm. However, for our purposes we will use the terms upper arm and forearm. Below are detailed diagrams and information regarding the arm bones (upper arm bones and forearm bones). Learn the names of the arm bones and arm anatomy trough the arm bones diagram. List of all Arm Bones extensor primi internodii pollicis and the pronator teres muscles Furthermore, the radius is found on each arm thus contributing a total of two bones to the human body skeleton. Ulna The ulna is the third and final bone of the arm. This bone runs parallel to the radius from the elbow to the wrist. Like the other arm bones, the ulna is relatively long and slightly curved. The primary function of the ulna is allowing motion and supporting the arm. An ulna exists on each arm and thus contributes two bones to the total human body skeleton. The ulna is also the site of attachment for many muscles and ligaments.

Examples of muscles attaching to the ulna include the triceps brachii muscle Radius and Ulna Radius and Ulna Science Main Index The arm consists of three large bones. The humerus bone forms the upper arm. The radius and ulna are the two bones forming the lower arm. You have one radius and one ulna in each arm. The radius and ulna bones connect between the elbow joint and the wrist. One easy way to remember which bone is the radius, and which is the ulna, is that the radius connects to the thumb side of the wrist. Keep reading to learn more about the radius and ulna, and how your lower arm works. On this page: Top of Page The lower arm consists of two bones extending from the elbow to the wrist, running parallel to each other. The radius is on the outside, or lateral side, of the elbow. It connects to the thumb side of the wrist. The radius is bigger and longer than the ulna which is on the inside, or medial side, of the forearm closest to the body. The bony point of the elbow, that most people think of as the elbow, is actually the tip the ulna bone.

The radius and ulna connect to the humerus bone of the upper arm at the elbow joint . Thehe elbow joint consists of a series of muscles or ligaments acting like a hinge so you can bend and straighten your arm. This is bending and straighten is called flexing and extending the arm, respectively. The elbow also provides for rotation of the lower arm through twisting of the radius and ulna. This twisting allows you to turn your hand palm up or palm down. The rotation of the lower arm is called pronation or supination depending on the direction of movement. Normally, the radius and ulna are parallel to each other. During pronation, the radius rolls around the ulna at both the wrist and the elbow. In this position, the radius and ulna appear crossed. Here is an experiment. You can actually feel the radius and ulna rotating. Hold your right forearm with your left hand. Then rotate your right wrist palm up and then palm down. You will feel the radius and ulna bones in your right arm twisting and rotating. II. Osteology. 6a. 4. The Ulna. Gray, Henry. 1918. Anatomy of the Human Body.

(Elbow Bone) 56 The ulna ( Figs. 212, 213 ) is a long bone, prismatic in form, placed at the medial side of the forearm, parallel with the radius. It is divisible into a body and two extremities. Its upper extremity, of great thickness and strength, forms a large part of the elbow-joint; the bone diminishes in size from above downward, its lower extremity being very small, and excluded from the wrist-joint by the interposition of an articular disk. 1 The Upper Extremity (proximal extremity) (Fig. 212 ).The upper extremity presents two curved processes, the olecranon and the coronoid process; and two concave, articular cavities, the semilunar and radial notches. 2 The Olecranon (olecranon process).The olecranon is a large, thick, curved eminence, situated at the upper and back part of the ulna. It is bent forward at the summit so as to present a prominent lip which is received into the olecranon fossa of the humerus in extension of the forearm.

Its base is contracted where it joins the body and the narrowest part of the upper end of the ulna. Its posterior surface, directed backward, is triangular, smooth, subcutaneous, and covered by a bursa. Its superior surface is of quadrilateral form, marked behind by a rough impression for the insertion of the Triceps brachii; and in front, near the margin, by a slight transverse groove for the attachment of part of the posterior ligament of the elbow-joint. Its anterior surface is smooth, concave, and forms the upper part of the semilunar notch. Its borders present continuations of the groove on the margin of the superior surface; they serve for the attachment of ligaments, viz., the back part of the ulnar collateral ligament medially, and the posterior ligament laterally. From the medial border a part of the Flexor carpi ulnaris arises; while to the lateral border the Anconæus is attached. FIG. 212 Upper extremity of left ulna. Lateral aspect.

( See enlarged image ) The Coronoid Process (processus coronoideus).The coronoid process is a triangular eminence projecting forward from the upper and front part of the ulna. Its base is continuous with the body of the bone, and of considerable strength. Its apex is pointed, slightly curved upward, and in flexion of the forearm is received into the coronoid fossa of the humerus. Its upper surface is smooth, concave, and forms the lower part of the semilunar notch. Its antero-inferior surface is concave, and marked by a rough impression for the insertion of the Brachialis. At the junction of this surface with the front of the body is a rough eminence, the tuberosity of the ulna, which gives insertion to a part of the Brachialis; to the lateral border of this tuberosity the oblique cord is attached. Its lateral surface presents a narrow, oblong, articular depression, the radial notch. Its medial surface, by its prominent, free margin, serves for the attachment of part of the ulnar collateral ligament.

At the front part of this surface is a small rounded eminence for the origin of one head of the Flexor digitorum sublimis; behind the eminence is a depression for part of the origin of the Flexor digitorum profundus; descending from the eminence is a ridge which gives origin to one head of the Pronator teres. Frequently, the Flexor pollicis longus arises from the lower part of the coronoid process by a rounded bundle of muscular fibers. 4 The Semilunar Notch (incisura semilunaris; greater sigmoid cavity).The semilunar notch is a large depression, formed by the olecranon and the coronoid process, and serving for articulation with the trochlea of the humerus. About the middle of either side of this notch is an indentation, which contracts it somewhat, and indicates the junction of the olecranon and the coronoid process. The notch is concave from above downward, and divided into a medial and a lateral portion by a smooth ridge running from the summit of the olecranon to the tip of the coronoid process.

The medial portion is the larger, and is slightly concave transversely; the lateral is convex above, slightly concave below. 5 The Radial Notch (incisura radialis; lesser sigmoid cavity).The radial notch is a narrow, oblong, articular depression on the lateral side of the coronoid process; it receives the circumferential articular surface of the head of the radius. It is concave from before backward, and its prominent extremities serve for the attachment of the annular ligament. 6 The Body or Shaft (corpus ulnæ).The body at its upper part is prismatic in form, and curved so as to be convex behind and lateralward; its central part is straight; its lower part is rounded, smooth, and bent a little lateralward. It tapers gradually from above downward, and has three borders and three surfaces. 7 Borders.The volar border (margo volaris; anterior border) begins above at the prominent medial angle of the coronoid process, and ends below in front of the styloid process.

Its upper part, well-defined, and its middle portion, smooth and rounded, give origin to the Flexor digitorum profundus; its lower fourth serves for the origin of the Pronator quadratus. This border separates the volar from the medial surface. 8 The dorsal border (margo dorsalis; posterior border) begins above at the apex of the triangular subcutaneous surface at the back part of the olecranon, and ends below at the back of the styloid process; it is well-marked in the upper three-fourths, and gives attachment to an aponeurosis which affords a common origin to the Flexor carpi ulnaris, the Extensor carpi ulnaris, and the Flexor digitorum profundus; its lower fourth is smooth and rounded. This border separates the medial from the dorsal surface. 9 The interosseous crest (crista interossea; external or interosseous border) begins above by the union of two lines, which converge from the extremities of the radial notch and enclose between them a triangular space for the origin of part of the Supinator; it ends below at the head of the ulna.

Its upper part is sharp, its lower fourth smooth and rounded. This crest gives attachment to the interosseous membrane, and separates the volar from the dorsal surface. Surfaces.The volar surface (facies volaris; anterior surface), much broader above than below, is concave in its upper three-fourths, and gives origin to the Flexor digitorum profundus; its lower fourth, also concave, is covered by the Pronator quadratus. The lower fourth is separated from the remaining portion by a ridge, directed obliquely downward and medialward, which marks the extent of origin of the Pronator quadratus. At the junction of the upper with the middle third of the bone is the nutrient canal, directed obliquely upward. FIG. 213 Bones of left forearm. Anterior aspect. ( See enlarged image ) FIG. 214 Bones of left forearm. Posterior aspect. ( See enlarged image ) The dorsal surface (facies dorsalis; posterior surface) directed backward and lateralward, is broad and concave above; convex and somewhat narrower in the middle; narrow, smooth, and rounded below.

On its upper part is an oblique ridge, which runs from the dorsal end of the radial notch, downward to the dorsal border; the triangular surface above this ridge receives the insertion of the Anconæus, while the upper part of the ridge affords attachment to the Supinator. Below this the surface is subdivided by a longitudinal ridge, sometimes called the perpendicular line, into two parts: the medial part is smooth, and covered by the Extensor carpi ulnaris; the lateral portion, wider and rougher, gives origin from above downward to the Supinator, the Abductor pollicis longus, the Extensor pollicis longus, and the Extensor indicis proprius. FIG. 215 Plan of ossification of the ulna. From three centers. ( See enlarged image ) FIG. 216 Epiphysial lines of ulna in a young adult. Lateral aspect. The lines of attachment of the articular capsules are in blue.

( See enlarged image ) The Lower Extremity (distal extremity).The lower extremity of the ulna is small, and presents two eminences; the lateral and larger is a rounded, articular eminence, termed the head of the ulna; the medial, narrower and more projecting, is a non-articular eminence, the styloid process. The head presents an articular surface, part of which, of an oval or semilunar form, is directed downward, and articulates with the upper surface of the triangular articular disk which separates it from the wrist-joint; the remaining portion, directed lateralward, is narrow, convex, and received into the ulnar notch of the radius. The styloid process projects from the medial and back part of the bone; it descends a little lower than the head, and its rounded end affords attachment to the ulnar collateral ligament of the wrist-joint. The head is separated from the styloid process by a depression for the attachment of the apex of the triangular articular disk, and behind, by a shallow groove for the tendon of the Extensor carpi ulnaris.

14 Structure.The long, narrow medullary cavity is enclosed in a strong wall of compact tissue which is thickest along the interosseous border and dorsal surface. At the extremities the compact layer thins. The compact layer is continued onto the back of the olecranon as a plate of close spongy bone with lamellæ parallel. From the inner surface of this plate and the compact layer below it trabeculæ arch forward toward the olecranon and coronoid and cross other trabeculæ, passing backward over the medullary cavity from the upper part of the shaft below the coronoid. Below the coronoid process there is a small area of compact bone from which trabeculæ curve upward to end obliquely to the surface of the semilunar notch which is coated with a thin layer of compact bone. The trabeculæ at the lower end have a more longitudinal direction. 15 Ossification ( Figs. 215, 216 ).The ulna is ossified from three centers: one each for the body, the inferior extremity, and the top of the olecranon.

Ossification begins near the middle of the body, about the eighth week of fetal life, and soon extends through the greater part of the bone. At birth the ends are cartilaginous. About the fourth year, a center appears in the middle of the head, and soon extends into the styloid process. About the tenth year, a center appears in the olecranon near its extremity, the chief part of this process being formed by an upward extension of the body. The upper epiphysis joins the body about the sixteenth, the lower about the twentieth year. The Ulna - Human Anatomy (Elbow Bone) (* 56 The ulna (Figs. 212, 213) is a long bone, prismatic in form, placed at the medial side of the forearm, parallel with the radius. It is divisible into a body and two extremities. Its upper extremity, of great thickness and strength, forms a large part of the elbow-joint; the bone diminishes in size from above downward, its lower extremity being very small, and excluded from the wrist-joint by the interposition of an articular disk. The Upper Extremity (proximal extremity) (Fig.

212).The upper extremity presents two curved processes, the olecranon and the coronoid process; and two concave, articular cavities, the semilunar and radial notches. The Olecranon (olecranon process).The olecranon is a large, thick, curved eminence, situated at the upper and back part of the ulna. It is bent forward at the summit so as to present a prominent lip which is received into the olecranon fossa of the humerus in extension of the forearm. Its base is contracted where it joins the body and the narrowest part of the upper end of the ulna. Its posterior surface, directed backward, is triangular, smooth, subcutaneous, and covered by a bursa. Its superior surface is of quadrilateral form, marked behind by a rough impression for the insertion of the Triceps brachii; and in front, near the margin, by a slight transverse groove for the attachment of part of the posterior ligament of the elbow-joint. Its anterior surface is smooth, concave, and forms the upper part of the semilunar notch.

Its borders present continuations of the groove on the margin of the superior surface; they serve for the attachment of ligaments, viz., the back part of the ulnar collateral ligament medially, and the posterior ligament laterally. From the medial border a part of the Flexor carpi ulnaris arises; while to the lateral border the Anconæus is attached. The Coronoid Process (processus coronoideus).The coronoid process is a triangular eminence projecting forward from the upper and front part of the ulna. Its base is continuous with the body of the bone, and of considerable strength. Its apex is pointed, slightly curved upward, and in flexion of the forearm is received into the coronoid fossa of the humerus. Its upper surface is smooth, concave, and forms the lower part of the semilunar notch. Its antero-inferior surface is concave, and marked by a rough impression for the insertion of the Brachialis.

At the junction of this surface with the front of the body is a rough eminence, the tuberosity of the ulna, which gives insertion to a part of the Brachialis; to the lateral border of this tuberosity the oblique cord is attached. Its lateral surface presents a narrow, oblong, articular depression, the radial notch. Its medial surface, by its prominent, free margin, serves for the attachment of part of the ulnar collateral ligament. At the front part of this surface is a small rounded eminence for the origin of one head of the Flexor digitorum sublimis; behind the eminence is a depression for part of the origin of the Flexor digitorum profundus; descending from the eminence is a ridge which gives origin to one head of the Pronator teres. Frequently, the Flexor pollicis longus arises from the lower part of the coronoid process by a rounded bundle of muscular fibers.

The Semilunar Notch (incisura semilunaris; greater sigmoid cavity).The semilunar notch is a large depression, formed by the olecranon and the coronoid process, and serving for articulation with the trochlea of the humerus. About the middle of either side of this notch is an indentation, which contracts it somewhat, and indicates the junction of the olecranon and the coronoid process. The notch is concave from above downward, and divided into a medial and a lateral portion by a smooth ridge running from the summit of the olecranon to the tip of the coronoid process. The medial portion is the larger, and is slightly concave transversely; the lateral is convex above, slightly concave below. The Radial Notch (incisura radialis; lesser sigmoid cavity).The radial notch is a narrow, oblong, articular depression on the lateral side of the coronoid process; it receives the circumferential articular surface of the head of the radius. It is concave from before backward, and its prominent extremities serve for the attachment of the annular ligament.

The Body or Shaft (corpus ulnæ).The body at its upper part is prismatic in form, and curved so as to be convex behind and lateralward; its central part is straight; its lower part is rounded, smooth, and bent a little lateralward. It tapers gradually from above downward, and has three borders and three surfaces. Borders.The volar border (margo volaris; anterior border) begins above at the prominent medial angle of the coronoid process, and ends below in front of the styloid process. Its upper part, well-defined, and its middle portion, smooth and rounded, give origin to the Flexor digitorum profundus; its lower fourth serves for the origin of the Pronator quadratus. This border separates the volar from the medial surface.

The dorsal border (margo dorsalis; posterior border) begins above at the apex of the triangular subcutaneous surface at the back part of the olecranon, and ends below at the back of the styloid process; it is well-marked in the upper three-fourths, and gives attachment to an aponeurosis which affords a common origin to the Flexor carpi ulnaris, the Extensor carpi ulnaris, and the Flexor digitorum profundus; its lower fourth is smooth and rounded. This border separates the medial from the dorsal surface. The interosseous crest (crista interossea; external or interosseous border) begins above by the union of two lines, which converge from the extremities of the radial notch and enclose between them a triangular space for the origin of part of the Supinator; it ends below at the head of the ulna. Its upper part is sharp, its lower fourth smooth and rounded. This crest gives attachment to the interosseous membrane, and separates the volar from the dorsal surface.

Surfaces.The volar surface (facies volaris; anterior surface), much broader above than below, is concave in its upper three-fourths, and gives origin to the Flexor digitorum profundus; its lower fourth, also concave, is covered by the Pronator quadratus. The lower fourth is separated from the remaining portion by a ridge, directed obliquely downward and medialward, which marks the extent of origin of the Pronator quadratus. At the junction of the upper with the middle third of the bone is the nutrient canal, directed obliquely upward. FIG. 213 Bones of left forearm. Anterior aspect. FIG. 214 Bones of left forearm. Posterior aspect. The dorsal surface (facies dorsalis; posterior surface) directed backward and lateralward, is broad and concave above; convex and somewhat narrower in the middle; narrow, smooth, and rounded below. On its upper part is an oblique ridge, which runs from the dorsal end of the radial notch, downward to the dorsal border; the triangular surface above this ridge receives the insertion of the Anconæus, while the upper part of the ridge affords attachment to the Supinator.

Below this the surface is subdivided by a longitudinal ridge, sometimes called the perpendicular line, into two parts: the medial part is smooth, and covered by the Extensor carpi ulnaris; the lateral portion, wider and rougher, gives origin from above downward to the Supinator, the Abductor pollicis longus, the Extensor pollicis longus, and the Extensor indicis proprius. The medial surface (facies medialis; internal surface) is broad and concave above, narrow and convex below. Its upper three-fourths give origin to the Flexor digitorum profundus; its lower fourth is subcutaneous. FIG. 215 Plan of ossification of the ulna. From three centers. FIG. 216 Epiphysial lines of ulna in a young adult. Lateral aspect. The lines of attachment of the articular capsules are in blue.

The Lower Extremity (distal extremity).The lower extremity of the ulna is small, and presents two eminences; the lateral and larger is a rounded, articular eminence, termed the head of the ulna; the medial, narrower and more projecting, is a non-articular eminence, the styloid process. The head presents an articular surface, part of which, of an oval or semilunar form, is directed downward, and articulates with the upper surface of the triangular articular disk which separates it from the wrist-joint; the remaining portion, directed lateralward, is narrow, convex, and received into the ulnar notch of the radius. The styloid process projects from the medial and back part of the bone; it descends a little lower than the head, and its rounded end affords attachment to the ulnar collateral ligament of the wrist-joint. The head is separated from the styloid process by a depression for the attachment of the apex of the triangular articular disk, and behind, by a shallow groove for the tendon of the Extensor carpi ulnaris.

Structure.The long, narrow medullary cavity is enclosed in a strong wall of compact tissue which is thickest along the interosseous border and dorsal surface. At the extremities the compact layer thins. The compact layer is continued onto the back of the olecranon as a plate of close spongy bone with lamellæ parallel. From the inner surface of this plate and the compact layer below it trabeculæ arch forward toward the olecranon and coronoid and cross other trabeculæ, passing backward over the medullary cavity from the upper part of the shaft below the coronoid. Below the coronoid process there is a small area of compact bone from which trabeculæ curve upward to end obliquely to the surface of the semilunar notch which is coated with a thin layer of compact bone. The trabeculæ at the lower end have a more longitudinal direction. Ossification (Figs. 215, 216).The ulna is ossified from three centers: one each for the body, the inferior extremity, and the top of the olecranon.

Ossification begins near the middle of the body, about the eighth week of fetal life, and soon extends through the greater part of the bone. At birth the ends are cartilaginous. About the fourth year, a center appears in the middle of the head, and soon extends into the styloid process. About the tenth year, a center appears in the olecranon near its extremity, the chief part of this process being formed by an upward extension of the body. The upper epiphysis joins the body about the sixteenth, the lower about the twentieth year. Articulations.The ulna articulates with the humerus and radius. Note 56. In the anatomical position, the forearm is placed in extension and supination with the palm looking forward and the thumb on the outer side. [ back ] Difference Between Radius and Ulna | Radius vs Ulna Home / Health / Medicine / Anatomy / Difference Between Radius and Ulna Difference Between Radius and Ulna Posted on Radius vs Ulna The human skeletal system is basically made up of bones, cartilages, tendons and ligaments.

It makes the framework of the human body, hence maintains the body shape and provides sites to attach muscles in the body. More than 90 % of the skeletal system is made up of bones. There are 206 bones in the human skeleton. Radius and ulna are two major bones in the lower arm and responsible to connect elbow and wrist. These two bones run parallel to each other, and are articulate with the humerus at the proximal ends while, connect with the wrist bones at the distal ends. The entire length of both bones is connected along by the interosseus membrane. Radius Radius is the lateral bone of the forearm when considering the anatomical position. It is wide at its distal, and narrow at its proximal end. The disc shaped proximal end of radius or the head of radius articulates with capitulum of humerus, whereas the distal end articulates with the wrist bones. Next to head is known as neck of the radius. Distal to the neck is the radial tuberosity where the muscles attach in order to permit flexion of the forearm. The long section of the radius is called the shaft.

Ulna articulates to the radius at the ulnar notch, which is an expanded portion of the radius. Anchoring sites of the radius at the lateral margin is called styloid process. Ulna If we consider the anatomical position, ulna is medial to radius in forearm. Ulna forms the elbow joint with humerus at its proximal end with its olecranon process. The concave depression on the anterior side of ulna is known as the trochlea notch, where the trochlea of the humerus articulates at the elbow joint. Coronoid process at the inferior end of the depression cavity joins with the trochlea of the humerus during extreme flexion. The ulna tuberosity is the attaching point of muscles, and radial point serves as the point where the head of radius articulates. Articular cartilage separates the head of ulna from wrist bones. Radius vs Ulna • Ulna is slightly larger than the radius. • Radius is narrow at its proximal end and wide at its distal end, whereas ulna has the opposite shape of radius. • In anatomical position, radius is the lateral bone of the forearm, and ulna is medial to radius.

• Disc shaped head of ulna is present at the distal end, whereas that of radius is present at the proximal end. Related posts: Ulna Anatomy 2D Interactive 3D Rotate & Zoom Change Anatomical System Change View Angle Full Ulna Description [Continued from above] . . . The olecranon fits into a small recess in the humerus known as the olecranon fossa, preventing the elbow’s extension beyond around 180 degrees. Just distal to the olecranon is the concave trochlear notch that surrounds the trochlea of the humerus to form the hinge of the elbow joint. The distal lip of the trochlear notch protrudes anteriorly to form the coronoid process that helps to lock the ulna in place with the humerus at the elbow and fits into the coronoid fossa of the humerus. On the lateral edge of the coronoid process is the small radial notch that forms the proximal radioulnar joint with the radius and permits the radius to rotate around the ulna at the elbow.

A long ridge on the anterior side of the coronoid process known as the ulnar tuberosity extends down the shaft of the ulna as a muscle attachment point. Moving distally from the elbow, the ulna begins to taper slightly in diameter along its entire length while curving medially. At its distal end, the ulna forms a small part of the wrist with the radius and the carpals of the hand. A rounded process known as the head of the ulna forms the distal radioulnar joint with the concave ulnar notch of the radius. The alignment of these joint-forming processes allows the radius to rotate around the ulna at the wrist. A small bony extension known as the styloid process protrudes from the posterior and medial corner of the ulna and provides an attachment point for the ulnar collateral ligament of the wrist. Functionally, the ulna provides muscle attachment sites for over a dozen muscles in the upper arm and forearm. In the upper arm, the triceps brachii and anconeus muscles form insertions at the olecranon to extend the forearm at the elbow. The brachialis muscle has its insertion on the coronoid process to flex the arm at the elbow.

Many muscles that act on the hand and wrist have their origins on the ulna, including the pronators, supinators, flexors and extensors. Like its neighbors the humerus and radius, the ulna is classified as a long bone because of its long, narrow shape. All long bones have a similar structure, with a hollow shaft surrounded by compact bone and reinforced at the ends with spongy bone. The hollow medullary cavity at the center of the ulna is filled with a soft, greasy substance known as yellow bone marrow. Yellow bone marrow contains many adipocytes and stores energy for the body in the form of triglycerides, or fats. Surrounding the medullary cavity is the hard, dense compact bone made of mineral matrix and collagen fibers. The mix of collagen and minerals, including calcium, gives the ulna its great strength and flexibility. The ends of the ulna are reinforced by spongy bone that increases the strength of the compact bone near the joints without significantly increasing the mass of the bone. Each region of spongy bone is made of many thin columns known as trabeculae that act like the steel girders of a bridge to withstand the stresses placed on the bone.

Red bone marrow is found in the spaces between the trabeculae and contains many stem cells that produce the body’s blood cells. On the joint-forming ends of the ulna are thin layers of hyaline cartilage that cover the compact bone and protect it from the stresses at the joints. Hyaline is as smooth as ice to help bones glide past each other at the joints. It is also rubbery to absorb the shocks of impacts at the joints. The outer surface of the ulna (except at the joints) is covered in a thin fibrous layer known as the periosteum. Periosteum is made of a dense weave of collagen fibers that extend into the tendons and ligaments that attach the ulna to the muscles and bones of the arm. The ulna begins at birth as a long bony shaft, known as the diaphysis, capped with hyaline cartilage at both ends. At around 4 years of age, the hyaline at the distal end by the wrist begins to ossify and forms a small bony cap known as the distal epiphysis.

A thin layer of hyaline, known as the epiphyseal plate or growth plate, remains between the diaphysis and the newly formed epiphysis. The ulna grows lengthwise into the growth plate, which in turn grows to prevent the fusion of the diaphysis and epiphysis. At around age 10, the proximal tip of the olecranon begins to ossify and forms the proximal epiphysis. These three bones continue to grow and remain separated by the epiphyseal plates until the end of puberty and the beginning of adulthood, when they fuse together to form a single, unified ulna. The site of the epiphyseal plate becomes known as the metaphysis in the mature bone. Prepared by Tim Taylor, Anatomy and Physiology Instructor Top 10 Longest Bones In The Human Body Top 10 Longest Bones In The Human Body 1 - Femur Average length : 19.88 in / 50.50 cm The femur is the only bone in the thigh. The femur is the longest, heaviest and by most measures the strongest bone in the human body. Its length is 26% of the person's height.

2 - Tibia Average length : 16.94 in / 43.03 cm The tibia also known as the shinbone or shankbone, is the larger and stronger of the two bones in the leg below the knee and it connects the knee with the ankle bones. In human anatomy the tibia is the second largest bone next to the femur. 3 - Fibula Average length : 15.94 in / 40.50 cm The fibula or calf bone is a leg bone located on the lateral side of the tibia, with which it is connected above and below. 4 - Humerus Average length : 14.35 in / 36.46 cm The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow. 5 - Ulna Average length : 11.10 in / 28.20 cm The ulna or elbow bone is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller.

The ulna is located at the side of the forearm closest to the body, the side of the little finger. 6 - Radius Average length : 10.40 in / 26.42 cm The radius or radial bone is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna, which exceeds it in length and size. 7 - 7th Rib Average length : 9.45 in / 24.00 cm Ribs are the long curved bones which form the cage. Ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the chest cavity. They serve to protect the lungs, heart, and other internal organs of the thorax. Humans have 24 ribs (12 pairs). The first seven sets of ribs, known as "true ribs". In general, human ribs increase in length from ribs 1 through 7 and decrease in length again through rib 12.

8 - 8th Rib Average length : 9.06 in / 23.00 cm 9 - Innominate Average length : 7.28 in / 18.50 cm The innominate bone also called hip bone or coxal bone is a large, Flat bone, constricted in the center and expanded above and below. The hip bone forms the primary connection between the bones of the lower limb and the axial skeleton. The hip bone is formed by three bones; ilium, ischium, and pubis. 10 - Sternum Average length : 6.69 in / 17.00 cm The sternum or breastbone is a long flat bony plate shaped like a capital "T" located anteriorly to the heart in the center of the thorax (chest). It connects to the rib bones via cartilage, forming the anterior section of the rib cage with them, and thus helps to protect the lungs, heart and major blood vessels from physical trauma.

Elbow Bones Top of Page Elbow - Lateral or Side View The elbow, or elbow joint, is formed by the connection of three bones: the humerus in the upper arm, and the radius and ulna in the lower arm. The bony point of the elbow, that most people think of as the elbow, is actually the tip the ulna bone. The humerus, radius and ulna are held together through a series of muscles or ligaments. These muscles allow the elbow to act like a hinge, so the arm can be bent and straightened. This is called flexing and extending the arm, respectively. The elbow also provides for rotation of the lower arm through twisting of the radius and ulna. With help from the wrist, this twisting allows you to turn your hand palm up or palm down. The rotation of the lower arm is called pronation or supination depending on the movement. Normally, the radius and ulna are parallel to each other. During pronation, the radius rolls around the ulna at both the wrist and the elbow. In this position, the radius and ulna appear crossed. Here is an experiment. You can actually feel the radius and ulna rotating. Hold your right forearm with your left hand.

Then rotate your right wrist palm up and then palm down. You will feel the radius and ulna bones in your right arm twisting and rotating. You often need to combine flexing and rotating to move your arm in complex ways. For example, you need to both flex and rotate your arm when you pick up food and put it in your mouth. Try it and watch how your arm moves. Anatomy/Terminology - Wikiversity Anatomy/Terminology Anatomical Position[ edit ] When discussing the anatomy of the human body, it is useful to first define a standard position in which the body will be presented. This standard allows the relative position of parts of the body to be described accurately and with less confusion. Anatomists use the anatomical position . A person in the anatomical position is standing up straight, with arms at the sides and palms facing forwards with the fingers extended. The feet are facing forward, as are the head and eyes (see the figure to the right). The anatomical planes of the body. Planes of the Body[ edit ] Three planes through the body are used to describe the position and orientation of parts of the body.

These are: Median or Sagittal plane - This plane runs through the body from the head (cephalic end) to the feet (plantar end). A cut on the sagittal plane of humans creates a right and left bilaterally symmetrical half. Any plane parallel to this through the body is known as a para-sagittal plane. Coronal plane/lateral/frontal - This plane runs through the body, also from the head to the feet, and divides the body into front and rear halves. Transverse plane - This is any plane that runs left to right through the body and divides it into upper and lower sections. Oblique plane - Any plane through the body that is not parallel to one of the former three. Anatomical Terms[ edit ] When discussing anatomy, the following terms are used to describe the relative positions of the parts of the body. When using these terms, it is assumed that the body is in the anatomical position. Lateral - More distant to the body midline. In the anatomical position, the radius is lateral to the ulna. A simpler example is the "thumb" is lateral to the "pinky." Medial - Closer to the midline; on the inner side.

The sternum (breast plate) is medial to the clavcle (shoulder bone). Superior - Above, towards the cephalic (head) end. The cranial cavity (head cavity) is superior to the scapula (shoulder blade). Inferior - Below, towards the plantar (foot) end. The patella (knee cap) is inferior to the femur (thigh bone). Anterior - Towards the front of the body. The sternum is anterior to the spine. Also known as ventral, but this term is not as common in human anatomy. Posterior - Towards the rear/backside of the body. The fibula is posterior to the tibia. Also known as dorsal, but this term is not as common. Superficial - Closer to the skin, nearer the body surface. Skin is superficial to the organs. Deep - Further from the body surface. In the limbs, the following terms are also used: Distal - Further from the limb's attachment to the trunk (where 'trunk' refers to the 'torso' of the body: the body minus the head, kneck, and limbs). proximal - Nearer to the limb's attachment to the trunk.

The humerous is proximal to the radius. Terms may also be combined to describe more complicated relative positions, for example anterolateral, meaning in front of and more lateral to something. Movement terms[ edit ] All acts of movement are considered to be a mixture or a single contribution of the following movement terms: Flexion - where there is a reduction in the angle between bones or parts of the body. This term applies only to movement along the sagittal or median plane. An example of arms flexing is lifting a dinner plate. When applied to the trunk of the body, this term means bowing forwards. Extension - is the opposite of flexion, and there is an increase in the angle. This term applies only to movement along the sagittal or median plane. With the trunk of the body, this movement is bowing backwards. Adduction - where there is a reduction in the angle between bones or parts of the body. This only applies to movement along the coronal plane. Abduction - the exact opposite, with an increase in the angle. Also only applies to movement along the coronal plane.An example of this is where extending arms outwards as if to fly.

Rotation - is rotation of an entire limb laterally (away from the body) or medially (towards the midline of the body). Pronation - this is the rotation of the hand so that the palm faces posteriorly. This is not medial rotation as this must be performed when the arm is half flexed. Prone means the hand is facing posteriorly. Supination - the rotation of the hand so that the palm faces anteriorly. The hand is supine (facing anteriorly) in the anatomical position. Protrusion - is the anterior movement of an object. This term is often applied to the jaw. Retrusion - the opposite of protrusion. Elevation - superior movement. This term is often applied to the shoulders (eg shrugging shoulders is elevation) Depression - inferior movement, opposite of elevation. Circumduction - is a special case of movement involving adduction, flexion, extension and abduction. The resulting movement creates a circular path of movement. Circumduction can be done in the hip, shoulder, thumb and fingers. Special cases[ edit ] There are several cases where the meaning of the anatomical planes and terms are slightly different. Hence new definitions for movement applies.

This is apparent in the foot, the tongue, the hand, the penis, the eyes, and the brain. Foot and hand[ edit ] The palm (adj palmar) of the hand corresponds to the sole (adj plantar) of the foot, and the dorsum (back) of the hand corresponds to the dorsum (top) of the foot. From this, the term dorsiflexion means to flex upwards (true extension) and the term plantarflexion, meaning to extend downwards (true flexion) are derived. The term volar, used mainly in orthopaedics, is synonymous with palmar and plantar. The foot is also capable of movement along another axis due to the flexibility of the ankle joint. These movements are Eversion - the movement of the sole of the foot away from the median plane. Inversion - the movement of the sole towards the median plane. (same as when an ankle is twisted). The position of the hand in anatomical position is considered supine, such that rotation of the hand so that the palm faces backwards is called pronation and the reverse action, supination. Others[ edit ] In the anatomical position, the penis is considered to be erect and pointing upwards, i.e.

the dorsal side of the penis is what one would normally call its top side (meaning the side that would touch the belly). The tongue has a dorsal side which is facing upwards (the side that tastes).

Question: In the human body which bone runs parallel to the ulna?
Answer: Radius